Objective: The aim was to assess the abdominal muscle activities during inspiration and expiration at different sitting positions in individuals with and without chronic low back pain (CLBP).

Methods: This study was conducted on 36 participants (18 with CLBP and 18 healthy controls). Ultrasound imaging was used to assess thickness changes of the transverse abdominis, internal oblique, rectus abdominis, and external oblique muscles. Muscle thickness was measured during inspiration and expiration under 3 different stability levels: sitting on a chair, sitting on a gym ball, and sitting on a gym ball with lifting the left foot. The muscle thickness measured in these positions was normalized to the actual muscle thickness at rest in supine lying and presented as a percentage of thickness change.

Results: Both groups displayed greater abdominal muscle activities as the stability of the surface decreased during both respiratory phases. However, compared with the healthy controls, the CLBP group showed smaller muscle thickness changes in all abdominal muscles, except the external oblique, in both respiration phases while sitting on a gym ball with lifting the left foot. The CLBP group displayed overactivity of the rectus abdominis muscle relative to the healthy controls while sitting on a chair in both respiratory phases.

Conclusion: The findings of the study indicate that as the stability of the support surface decreases, individuals with CLBP had more difficulty activating all abdominal muscles in a similar manner compared to healthy controls in both respiratory phases, which might affect both respiration and postural stability.

Author keywords: Chronic Pain; Muscle Thickness; Posture; Respiration; Ultrasonography

Author affiliations: OR: Department of Physiotherapy, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran; Department of Mental Health, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology, Trondheim, Norway; SS: Rehabilitation Research Center, Iran University of Medical Sciences, Tehran, Iran; AMA: Department of Physiotherapy, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran; SSA: Rehabilitation Research Center, Department of Physiotherapy, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran; HS: Department of Occupational Medicine, Faculty of Medicine, Clinical Developmental Research Center of Shahid Mohammadi Hospital, Hormozgan University of Medical Sciences, Bandar Abbas, Iran

This abstract is reproduced with the permission of the publisher; full text is available by subscription. Click on the above link and select a publisher from PubMed's LinkOut feature.